This invention relates to centrifugal blowers and fans.
Centrifugal blowers and fans generally include an impeller that rotates in a predetermined direction in a housing, and may be driven by an electric motor. The impeller has curved blades which draw air in axially, along the impeller's axis of rotation, and discharge air radially outwardly. Such blowers are used in a variety of applications, which dictate a variety of design points for pressure difference, airflow volume, motor power, motor speed, space constraints, inlet and outlet configuration, noise, and manufacturing tolerances.
One important design feature in a centrifugal fan is the angle of the blade tip relative to a tangent to the tip. This angle is called the "blade exit angle". If the blade exit angle is greater than 90.degree., the impeller is said to have forwardly curved blades; if the blade exit angle is less than 90.degree., the impeller is said to have rearwardly curved blades.
Specific centrifugal blowers described in prior patents are discussed below.
Koger et al., U.S. Pat. No. 4,526,506 and DE No. 2,210,271 disclose rearwardly curved centrifugal blowers with a volute.
GB No. 2,080,879 discloses a rearwardly curved centrifugal blower with stator vanes to convert radial flow to axial flow.
Zochfeld, U.S. Pat. No. 3,597,117 and GB No. 2,063,365 disclose forwardly curved centrifugal blowers with a volute.
Calabro, U.S. Pat. No. 3,967,874 discloses a blower 16 positioned in a plenum chamber 14. The blade configuration and blower design are not apparent, but opening 46 in the bottom of the plenum chamber is in communication with the blower outlet.
GB No. 2,166,494 discloses a centrifugal impeller in a rotationally symmetrical cone-shaped housing, with guide vanes to produce an axial discharge.
GB No. 1,483,455 and GB No. 1,473,919 disclose centrifugal blowers with a volute.
GB No. 1,426,503 discloses a centrifugal blower with dual openings.
Shikatani et al., U.S. Pat. No. 4,269,571 disclose a centripetal blower, which draws air in axial entrance 26 and out of the top periphery of disc 22 and axial exit 27 (3:26-36).
Canadian No. 1,157,902 discloses a rearwardly curved centrifugal blower with a curved sheet-metal guide.